An on-vehicle camera (hereinafter referred to as the stereo camera), serving as an on-vehicle image processing device, uses a pair of images captured by two imaging sections, calculates the distance to a target by triangulation, and recognizes the target accordingly, is now beginning to be applied to an on-vehicle system for facilitating safe driving of a vehicle.
In an environment where the device is mounted on vehicles, in particular, it is necessary to properly measure the distance to a remote target and recognize it due to application requirements that demand the detection of preceding vehicles, humans, and obstacles in order to take safety precautions.
Further, when a stereo image processing system is to be used as an on-vehicle system, it is also requested that the system be compact, low-priced, and highly reliable.
The above system generally includes a dedicated LSI that checks pixel information included in a pair of images, identifies positions of pixels indicative of feature points common to the pair of images, and determines the number of displaced pixels indicative of feature points in the pair of images (hereinafter referred to as disparity).
As the above principles apply, it is ideal that no displacement except disparity is found in the pair of images. All imaging means need to be structured so that they can be accurately adjusted to avoid any discrepancies in optical characteristics and signal characteristics and maintained in the accurately adjusted state.
An invention disclosed in Patent Document 1 is related to the above-described background art. Patent Document 1 describes that an on-vehicle camera formed of a pair of cameras includes a camera stay and an installation area. The installation area is structured integrally with the camera stay and fastened to a chassis of a vehicle, the camera stay holding the pair of cameras in predetermined positions. The on-vehicle camera is securely screwed into the installation holes in the chassis of the vehicle by use of three installation holes disposed in the installation area and of three screws. As the camera is screwed in this way, it is possible to accurately maintain the relative positions of the pair of cameras.
Patent Document 2 describes a compound-eye camera. Two or more light rays are emitted from two or more light sources disposed at a position at which the compound-eye camera is mounted. A target is disposed at an intersection of the two or more light sources. The compound-eye camera is adjusted by photographing the target. This adjustment makes it possible to accurately adjust the optical axis and focus of the compound-eye camera.